New P2-Na0.70Mn0.60Ni0.30Co0.10O2 Layered Oxide as Electrode Material for Na-Ion Batteries

Sodium layered oxide, Na0.70Mn0.60Ni0.30Co0.10O2, with a P2-type structure was synthesized by a co(-)precipitation method and characterized as positive electrode of sodium batteries. The P2-NaxMn0.60Ni0.30Co0.10O2 electrode delivered a high specific capacity of 185 mAh/g in the 1.5-4.3 V range at 1st cycle at C/20 rate; however, rapid capacity decay is observed. In the 1.7-4.0 V range the capacity is equal to 125 mAh/g with a fading considerably reduced. The rate capability is reasonably good. According to the electrochemical profile, a potential plateau around 4.2 V vs. Na+/Na, meaning a bi-phasic domain, and several voltage drops that could be related to single phase domains in a narrow sodium content range are observed. Even if the capacity decreases when the battery is cycled above 4.0 V, there is no irreversible structural change. (C) 2014 The Electrochemical Society. All rights reserved.